oil pumping problems

[edbaus]

Hi,

I have a question on my 3.6L motor problem. Here is the whole story.


This is in my race car. It is a stock motor except for upgraded cams. It is a 1990 motor that I just rebuilt (I am fairly experienced at rebuilding)

The oiling on my car runs from the motor, to a system 1 oil filter with an-16 ends on both sides (I have been using it for a year now with no issue), then to a pair of mocal filters (brand new) then to a front mounted tank. The breather at the top of the motor is vented to the front mounted tank.

OK, freash motor on the dyno. It made 258 rwhp. Spent at least 3-1/2 hours tuning the motor on the dyno. No issues at all. Checked the oil level in the tank while the motor was running and there was a half a tank as I am used to.

Went to the track this weekend. Friday it was cold and a little rainy. Got out for two sessions. The first session was a little wet, but the second was dry and I really was able to open it up. It ran great.

Saturday. Colder (low 50's) and still a little damp. Lined up to go out for the first session. The oil pressure fluctuated a little, so I checked the tank for level. There was no oil showing in the tank. I added 6 quarts to bring it to level. I went out and the car did not have power. The oil temp started to rise and before I could get back in, the distributor plug was ejected from the motor and oil sprayed all over. (still had good oil pressure all the way)

They brought me back in and I dumped the oil to find out where all of the oil from the tank went. All of the oil was in the case.

I took apart the oil filter it was crushed (oil enters the outside and exists to the opposite end from the inside). I removed the crushed cleanable element, so now there is nothing in the cylinder to slow the oil down. Put the right amount of oil in the car, started it up, and all the oil got sucked into the motor, then the oil started to get returned to the tank from the breather.

I have removed one, then the other, then both oil coolers from the circuit. By taking both off, the oil kind of returns but still spits out the breather.

I am thinking that maybe the oil filter getting crushed caused back pressure in the line that sheared the key in the oil pump so the gears are spinning on the shaft and not pumping the scavenge side of the oil back?

I am really open to ideas here. (before I drop and disassemble my motor)

Thanks

Ed

[edbaus]

So, I had a new thought last night.

Is it possible that under pressure (if the scavange pump was dead heading) that the rubber seal between the oil pump and the engine case ruptured ?

Ed

[WERK I]

My best guess is the dry sump pump housing is cracked or as you say a ruptured seal.

The scavenge side of the pump, if I remember correctly, will always draw more oil and the pressure side of the pump. If your observations are correct, you are seeing good oil pressure from the pressure side of the pump, but no scavenge. Correct?

[RSstop]

Ed,
I feel for you. A dead-headed gear pump will build pressure until something breaks. I think the pump seal blowing out is more likely than a sheared pump shaft. You would think that the by-pass relief circuit would protect it.
Do you run a thermostat? I am sure the cold viscous oil contributed to the problem.
If all lines are clear, you may have to split it.
Lyn

[304065]

Ed,

I think a teardown to inspect the oil pump is in order. My guess is that the combination of the cold oil, three filters and two coolers put too much of a load on the stock 964 oil pump, resulting in failure.

The "oil bypass mod" resulted in the scavenge pump being made smaller and the pressure stage made larger. But the later pumps have a BIG scavenge stage. I think the size of the gears is probably intended to equalize the flow given a constant supply of oil to the pressure side and an intermittent supply from the scavenge pickup in the bottom of the sump.

930 oil pump (930 107 008 04) now 996 107 008 70 (stock in Germany) now supercedes to 996-107-008-70 (996 Turbo Pump)-


964 oil pump 964 107 011 11 (stock in Germany)



GT3 oil pump 996 107 007 94


GT3 pump again

[edbaus]

Thanks guys.

A few answers to the questions.

I am not currently, but will be after this, be running a oil thermostat in the circuit.

I am still seeing good. Very good. oil pressure to the motor.


and a couple of questions.

I have an extra oil pump housing or two. Are the housings matched to the gears in them, or can I mix and match the bodies. (that is if the scavenge body is cracked)

My oil filter is between the oil pump and the oil coolers. Should I put the thermostat before the filter since the filter collapsed from the thick oil.

I am going to have it on the lift later today and get the oil out so I can see in the scavenge port to see what I can see. I should at least be able to tell if the seal is damaged or missing.

Thanks

Ed

[WERK I]

It acting like the filter is installed backwards. On most filters, there is a high pressure bypass to allow for oil flow around the filter when the oil is not up to operating temps and is thick(relatively speaking). In your case, the oil flow when cold, acts normal. But when it gets up to 190, the case starts filling up? BTW, the oil thermostat for the 911 front mounted oil coolers open up around 190.

Thermostat, the same thing, same type of scenario. Are you sure your plumbing for your oil lines is set up right?

[edbaus]

The car currently has no thermostat as I had mensioned.

The oil filter is installed with the flow in the direction of the flow arrows on the filter itself.

I will be adding a mocal thermostat in before the oil filter and coolers.

Thanks

Ed

[MBEngineering]

HI Ed
check the compression's and if poss' a cylinder leakage check, had a engine like that and it had a ring prob' caused by a faulty dist', did not find it until to late, hope it is OK and just a pluming prob'

regards mike

[dion914-6]

Hey Ed, wish I were up there to help out. Sounds like a real bummer. Find anything yet?

I blew up 2 formula vee engines because the oil filter housing was incorrectly cast with the wrong in/out arrows. The oil was building up at the filter, and in the Vee negine's case, starving the rods.

But it sounds like you were running this system last year on the 3.2 without any issues.

D

[edbaus]

Got the motor out and I am down to the p's and c's. I can see a crack in the body of the oil pump through one of the return tube holes.

Thanks. Yea, it was fine last year. Probably just too cold last weekend without a bypass. well on my way to having eveything done for the May 3rd, 4th Mid-Ohio drivers ed.

Ed

[304065]

Ed, how about a closeup of that cracked pump?

[edbaus]

Will do.

Thanks

Ed

[kenikh]

(Grady ) Is this something that is related to the all-aluminum pumps only? I recall recently reading about another similar story of a cracked oil pump; might have even been a 964 pump, too. Since the 930 pumps are half cast iron, do they crack?